Virucidal effect of chlorinated water containing cyanuric acid

The inhibitory influence of cyanuric acid on the virucidal effect of chlorine was studied. The time required for 99.9% inactivation of ten enteroviruses and two adenoviruses by 0.5 mg/l free available chlorine at pH 7.0 and 25 degrees C was prolonged approximately 4.8-28.8 times by the addition of 30 mg/l cyanuric acid. Comparative inactivation of poliovirus 1 by free available chlorine with or without cyanuric acid revealed the following. The inactivation rate by 1.5 mg/l free available chlorine with 30 mg/l cyanuric acid or by 0.5 mg/l free available chlorine with 1 mg/l cyanuric acid was slower than by 0.5 mg/l free available chlorine alone. Temperature and pH did not affect the inhibitory influence of cyanuric acid on the disinfectant action of chlorine. In the swimming-pool and tap water, cyanuric acid delayed the virucidal effect of chlorine as much as in the 'clean' condition of chlorine-buffered distilled water. The available chlorine value should be increased to 1.5 mg/l when cyanuric acid is used in swimming-pool water.